sedimentary

Quartz Pebble

Silicon Dioxide (SiO2)

Hardness: 7 Mohs; Color: Tan/Grey; Luster: Vitreous to dull; Crystal Structure: Hexagonal (cryptocrystalline in this form); Cleavage: None; Specific Gravity: 2.65

Hardness: 7 Mohs
Color: Tan/Grey
Luster: Vitreous to dull

Identified June 1, 2026More sedimentary →

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Physical properties

Hardness: 7 Mohs; Color: Tan/Grey; Luster: Vitreous to dull; Crystal Structure: Hexagonal (cryptocrystalline in this form); Cleavage: None; Specific Gravity: 2.65

Formation & geological history

Formed from the erosion of quartz-rich igneous or metamorphic rocks, followed by transport and rounding in a fluvial (river) or coastal environment. These are common in quaternary deposits.

Uses & applications

Commonly used as aggregate in construction, decorative gravel in landscaping, and as a source for silica in industrial glass manufacturing.

Geological facts

Quartz is the second most abundant mineral in Earth's continental crust. These small rounded stones are often called 'river rocks' due to the hydraulic action that smooths them.

Field identification & locations

Identify by its hardness (it will scratch glass) and lack of cleavage. Look for smooth, rounded shapes in stream beds, beaches, or glacial till deposits.